The Oceans
Salt water covers more than seven-tenths
of the Earth's surface. We now know that
there are high mountains, deep trenches and
volcanoes hidden from sight under the waves.

Ocean Facts
The Pacific, the biggest ocean, is larger
than all of the Earth's land area added together.
It covers about 166,241,000 sq km
( 64,186,000 sq miles ).The deepest place
in the sea is in the Marianas Trench in the
Pacific. The water there is 11,033 m ( 36,198
ft ) deep.

Ocean Tides and Currents
Tides are rises and falls in the sea
level
that occur twice every 24 hours, 50
minutes.
They are caused mainly by the moon.
When
the moon is overhead, its gravity pulls
the
water towards it, making the seas bulge.
Currents move water about and it is never
quite still, even in the deepest ocean. Surface
currents, mainly caused by winds, affect
only about the top 350 m
( 1,148 ft ) of water. Warm surface currents
flow from the Equator towards the Poles,
while deep cold polar ones move the other
way. The warm Gulf Stream, flowing across
the Atlantic, brings mild winters to northern
Europe and Iceland.